Language-Integrated Query (LINQ) is a set of features introduced in Visual Studio 2008 that extends powerful query capabilities to the language syntax of C# and Visual Basic. LINQ introduces standard, easily-learned patterns for querying and updating data, and the technology can be extended to support potentially any kind of data store. Visual Studio includes LINQ provider assemblies that enable the use of LINQ with .NET Framework collections, SQL Server databases, ADO.NET Datasets, and XML documents.
The MSDN Code Gallery includes LINQ Samples. As a convenience, here are several quick links to samples:
Provides an entry point for documentation about LINQ to DataSet, LINQ to SQL, and LINQ to Entities. LINQ to DataSet enables you to build richer query capabilities into DataSet by using the same query functionality that is available for other data sources. LINQ to SQL provides a run-time infrastructure for managing relational data as objects. LINQ to Entities enables developers to write queries against the Entity Framework conceptual model by using Visual Basic or Visual C#.